Southern California -- this just in

7.2 Mexicali earthquake made 2 other California faults riskier

July 2, 2010 | 8:06
am

Preliminary analysis shows that the 7.2 Mexicali earthquake in April placed more pressure
on at least two Southern California fault lines: the Elsinore and the
San Jacinto.

The Elsinore fault runs through portions of San Diego County, including
near Julian, as well as through Temecula and Lake Elsinore in Riverside
County; the San Jacinto fault runs near cities such as Hemet, Loma
Linda and San Bernardino.

Scientists say earthquakes now are more likely on those two faults, but
because so little is known about them, it's hard to calculate the risks.

Experts say the larger question is whether the temblor made quakes more
likely along more dangerous fault lines, such as the Whittier — which
produced the deadly 1987 Whittier Narrows quake — and the San Andreas.

Scientists are particularly interested in the Whittier fault because
it's connected to the Elsinore and runs under heavily populated areas.

On Thursday, NASA flew a specially equipped Gulfstream III jet over the
quake zone, looking for signs of Earth rupture that could help experts
understand how the various faults are connected.

There are several key clues scientists were looking for during the
nearly six-hour research flight, which covered such seismically active
areas as the Salton Sea and U.S.-Mexico border as well as the San Diego
coast. If data show slipping along the northern edges of the Mexican
fault that triggered the 7.2 quake, that would suggest that pressure is
being placed on faults in Southern California.

If they don't see significant slippage, it could suggest that the fault
has stabilized and there is less risk to faults in California. The
flight, one of several planned, produced photos and data that
scientists will analyze.

Photo: A passenger photographs a huge crack in a Mexican road near Mexicali left by the 7.2
earthquake in April, the largest quake in the region in
years. JPL scientists are studying data from the quake, trying to learn
how — or if — the quake affected other faults; credit: Don Bartletti / Los Angeles Times